Recently, interest in energy saving measures is increasing, and, for example, from the viewpoint of reducing the load on cooling equipment, there have been increased demands for an infrared shielding film which is mounted to a window glass of a building and a vehicle to block transmission of heat rays of sunlight.
As a method of infrared shielding film formation, there has been mainly proposed a method of forming a laminate unit constituted of alternately stacked high refractive index layers and low refractive index layers using a dry film-forming method such as a vapor deposition method and a sputtering method. However, in the dry film-forming method, a vacuum apparatus used in the formation is increased in size to increase manufacturing cost, and it is difficult to increase the area. In addition, there is a problem that a substrate is limited to a thermal-resistant material.
Recently, there is widely considered a method of forming an infrared shielding film using a wet coating method instead of the dry film-forming method having the above problems (Patent Literatures 1 to 3).
For example, Patent Literature 1 discloses a method of coating a high refractive index layer coating liquid, prepared by dispersing a thermosetting silicone resin containing fine particles of a metal compound such as metal oxide, an ultraviolet hardening acrylic resin, or the like in an organic solvent, onto a substrate using a wet coating method using a bar coater to form a transparent laminate. Patent Literature 2 discloses a method of coating a coating liquid for a high refractive index, constituted of rutile-type titanium dioxide, a heterocyclic nitrogen compound (for example, pyridine), an ultraviolet hardening binder, and an organic solvent, onto a substrate using a wet coating method using a bar coater to form a transparent laminate. Patent Literature 3 discloses a method of alternately stacking layers using a methanol-dispersed slurry of spherical rutile type titanium oxide particles and methanol silica sol.